Crazy! Only place I've seen close to that many Reds in one spot is around the ferry lights in Port Aransas. Started to wonder how you could film that and not drop a line in but he does by the end of the video.
Saw this a lot down by the old Aggie pier in Port A while fishing at night. Dolphins would corral the reds in to the little cove and start feeding. When they were done, the reds wouldn't leave so I would start throwing my bait in front of them.